Ceramic materials are widely used in many civil and military applications, including structural and functional applications. High temperature resistance and desirable mechanical properties are among the advantages of ceramic materials, while poor toughness and certain processing conditions required for their preparation may be among the disadvantages of ceramic materials. Nevertheless, for certain specific applications, such as fairings in missiles and airplanes, rocket nozzles, and some brake pads, ceramic materials may be preferred over other materials.
Bulk ceramic materials are typically fabricated by compacting and sintering ceramic powders. This process may require high quality ceramic powders (e.g., powders having dimensional and/or compositional uniformity), and/or certain treatment conditions (e.g., a cold isostatic press for the preform, and/or a high temperature hot press furnace for sintering), in order to obtain a final product having high integrity. Products with complex shapes also can be much more difficult to achieve.
Three-dimensional (3D) printing technologies have been developed for a wide variety of materials. Initially, the 3D technologies were capable of utilizing thermoplastics, but improvements in the technology have permitted the use of metals and earthenware. Recently, there have been experiments on food-, wood-, and bio-printing, indicating that the portfolio of materials that may be amenable to 3D printing is expanding.
3D printing generally is a favorable method of additive manufacturing, which may be an advantageous method of manufacturing when conservation of materials, time, and/or energy may be important. By extruding a material in thin lines and stacking each line layer by layer into a desired form, countless articles may be printed into a desired shape and/or geometry. 3D printing technology, therefore, has the potential to simplify highly specialized manufacturing methods in fields such as biomedical engineering, defense, and aerospace, at least because it typically utilizes only the material required for each product, and can eliminate or reduce the need for machining and other tedious secondary handling.
Attempts at 3D printing with ceramics have included dispersing ceramic powders into a polymeric binder to form a slurry. The polymeric binder typically is then removed in a sintering process (see, e.g., T. Huang, et al., Rapid Prototyping Journal, Vol. 15, No. 2, pp. 88-95, 2009; and M. C. Leu et al., Journal of Manufacturing Science and Engineering, Vol. 136, pp 061014 (1-9), 2014). A high-power mixer, however, usually is needed to disperse the ceramic powders sufficiently in the polymeric binder. Also, the sintering process, which usually occurs in a high temperature pressurized furnace, typically imparts open spaces in the manufactured article after the binder is removed. The open spaces may decrease the density of the article, adversely impact the characteristics of the article, or a combination thereof.
There remains a need for methods of additive manufacturing that are capable of taking advantage of one or more of the beneficial properties of ceramics without suffering at least one of the foregoing disadvantages, such as the difficulty of mixing ceramic powders sufficiently in a polymeric binder, the creation of porous and/or cracked articles, or a combination thereof.